Red Colobus are sometimes included in the genus Piliocolobus (e.g., Kingdon 1997; Groves 2001, 2005). The current treatment follows Grubb et al. (2003) in regarding Piliocolobus as a subgenus of the genus Procolobus, pending the availability of further evidence. Procolobus rufomitratus as defined here is very diverse comprising nine subspecies, some of which have been considered distinct species in the past.

Justification:
Listed as Least Concern as the species as a whole is widespread and not believed to be declining at any rate sufficient to warrant listing in a threatened category, although several subspecies are on the verge of extinction and in urgent need of conservation action. A number of the subspecies included here may actually represent distinct species in their own right.

North of the Congo River, this species ranges widely from about the River Sangha in the west to Lake Albert; south of the Congo River, it occurs as far south as the Kasai and Sankuru Rivers. Also occurs in isolated fragments (as P. r. tephrosceles) east of the Albertine Rift, and an isolated form, P. r. rufomitratus, persists on the lower Tana River in Kenya (Gautier-Hion et al. 1999; Struhsaker and Grubb in press). The species ranges from near sea-level to 2,500 m.

In this treatment, the species includes nine subspecies:

P. r. rufomitratus is found only on the levees of the lower Tana River in Kenya. The total known range is 60 km from Kipende in the north to Mitipani in the south, where the Lamu-Garsen road enters the Tana River floodplain. It is restricted to ca. 34 patches of fragmented gallery forest, notably Guru South, Sifa East, Baomo South, Mnazini East, Bubesa West 1, Hewani South 2 forests (Butynski and Mwangi 1994). P. r. rufomitratus is broadly sympatric with Cercocebus galeritus and Cercopithecus mitis albotorquatus, and narrowly sympatric on the forest edges with Papio cynocephalus ibeanus and Cercopithecus pygerythrus (T. Butynski and Y. de Jong pers. comm.).

P. r. tephrosceles is present on the eastern border of the Rift Valley in western Uganda and western Tanzania (Struhsaker and Grubb in press). Five distinct populations are known in western Uganda in Kibale, and in western Tanzania in Biharamulo on the south-western shores of Lake Victoria, Gombe and Mahale Mountains on the eastern shores of Lake Tanganyika, and Mbizi and Misheta on the Ufipa Plateau (Rodgers et al. 1984). However, recent surveys in Misheta found little if any forest left of any consequence in the area, and the red colobus population is probably now extinct there (Davenport et al. 2007). A subpopulation subsequently recorded in a forest patch near the village of Nsangu (post the surveys by Rodgers et al.) is probably also now extinct (Davenport et al. 2007). Davenport et al. (2007) reported a new and previously unrecorded population of P. r. tephrosceles in Mbuzi forest. They also surveyed the Chala forest, which was in poor condition; no primates were seen, although it is not known if red colobus ever existed there. This subspecies may be present in the eastern Democratic Republic of Congo, Rwanda and Burundi, but its presence has not yet been confirmed.

P. r. foai from Democratic Republic of the Congo between the Rivers Lowa and Osa in the north and about 6°S in the south along the western side of Lake Tanganyika (Struhsaker and Grubb in press).

P. r. oustaleti, occurs in Congo, southern Central African Republic, Democratic Republic of Congo and marginally in southern Sudan, from the River Sangha in the west across the Oubangui River east to Lake Albert; the southern border of its range is the Congo River, the eastern limit is the River Aruwimi-Ituri, and in the north its range extends into the savanna woodlands north of the River Uele (Gautier-Hion et al. 1999; Struhsaker and Grubb in press).

P. r. lulindicus is present in Democratic Republic of Congo in lowland forest east of the Lualaba River from the Lowa-Osa River in the north to the Elila River in the south (Struhsaker and Grubb in press).

P. r. langi occurs in pure form in the cul-de-sac between the Lualaba and Aruwimi-ituri Rivers in north-east Democratic Republic of Congo and extends as a variant within the population eastward to the vicinity of Lake Kivu (P. Grubb unpubl.).

P. r. ellioti ranges from Congo-Lualaba River east to the Semliki Valley, and the west shore of Lake Edward and Lake Kivu. The northern limit is the Aruwimi-Ituri River, and the southern limit the Maiko River (Struhsaker and Grubb in press).

P. r. parmentieri in the area between the Lomami and Lualaba Rivers in the Democratic Republic of Congo, as far south as the Rivers Ruiki and Lutanga (Colyn and Verheyen 1987; Struhsaker and Grubb in press).

P. r. tholloni is a little-known taxon that occurs in a patchy distribution from south of the great bend of the Congo River, west of the River Lomami, Democratic Republic of the Congo. Southern limits bounded by the Kasai and Sankuru Rivers (Struhsaker and Grubb in press). Except for P. r. parmentieri, this is the only red colobus taxon to occur south of the Congo River.

There are no overall population estimates for most of the forms of red colobus assigned to this species.

P. r. tephrosceles numbers at least 20,000 animals, with the largest and most viable population in Kibale Forest in Uganda where the population is estimated at ≥17,000 (Struhsaker 2005). Approximately 60% of the Kibale park represents suitable habitat for red colobus and published density estimates for them in this habitat range from 93-313/km² (Struhsaker 2005). Although Kibale would appear to have a healthy and viable population, long-term studies in two areas of the park indicate statistically significant declines in red colobus numbers. In the Ngogo study area, census data spanning nearly 24 years indicate a 43% decline in groups (Mitani et al. 2000), mainly due to Chimpanzee Pan troglodytes predation. A similar long-term study spanning 28 years at the Kanyawara site of Kibale also indicated a 40% decline in red colobus numbers within old growth and protected forest, as well as in nearby selectively logged forest (Chapman et al. 2000). Red colobus density in forest fragments on the western boundary of Kibale averaged 2.1 animals per hectare and ranged from 0 to 8.33 animals / ha (Chapman et al. 2006).

The red colobus in Gombe National Park also seem to have declined in numbers due to predation by Chimpanzees. Red colobus group sizes have declined by nearly 50% over a 25-year period (Stanford 1998) and 16–40% of them are killed each year by chimpanzees (Wrangham and Bergmann-Riss 1990).

Recent survey work by Davenport et al. (2007) shows that a total of at least 1,354 red colobus survive on the Ufipa Plateau, with 1,217 in Mbizi and 137 in Mbuzi.

The total population of P. r. rufomitratus is estimated at 1,100-1,300, down from an estimated 1,200-1,800 in 1975 (Butynski and Mwangi 1994, 1995; Mbora 2003). This is not considered a significant decrease and suggests that the species may have developed strategies to cope with the shrinking habitat. Recent surveys indicate at least 86 groups occur in 34 forest patches (Butynski and Mwangi 1994; Mbora 2003); mean group size has declined by about 50% since the 1970s (Struhsaker and Grubb in press; and refs therein). Densities of P. r. ufomitratus along the Tana River, Kenya have ranged from 33-253 individuals/per km² (Marsh 1978; Decker 1994; Mbora 2003).

P. r. oustaleti is likely to be among the more numerous of the Red Colobus taxa, given the size of the range (Struhsaker and Grubb in press). This was the third most observed species in the flooded forests of Ngotto Forest in south-western CAR (Brugiere et al. 2005).

This species occurs in a wide variety of forest types, including riverine and gallery forest (e.g., the nominate subspecies P. r. rufomitratus in Kenya, where the forests are dominated by Pachystela and Barringtonia), forest-miombo savanna mosaic, old-growth lowland, mid-altitude, and montane moist rain forest, degraded secondary forests, and raphia palm swamps (Struhsaker and Grubb in press).

In Kibale, P. r. tephrosceles is most abundant in moist, old-growth, evergreen forest with emergent trees reaching 50 m in height (Struhsaker and Grubb in press, and refs therein). It can persist in lightly logged forest as long as important food trees remain (Lee et al. 1988). Groups of P. r. tephrosceles average about 45-50 individuals in Kibale, and 55-59 individuals in Gombe (Struhsaker and Grubb in press, and refs therein). The mean group size recorded in Mbizi was 41 and in Mbuzi, 34 (Davenport et al. 2007).

P. r.oustaleti, the most widespread subspecies, is found in mature primary lowland tropical moist forest, swamp forest and gallery forest, as well as in in savanna woodland. However, in Ngotto Forest in Central African Republic, this species only occurs in flooded forests on alluvial river banks (Gautier-Hion and Brugiere 2005). Galat-Luong and Galat (1979) reported that they spent 30% of their time <10 m above ground and regularly enter into water to collect bulbs of aquatic plants.

In the Congo Basin, P. r. tholloni is common in flooded forests where they eat a lot of seeds (Maisels et al. 1994).

Across the range, localized declines are taking place due to ongoing habitat loss (mainly as a result of deforestation for timber and agricultural land), and from hunting for meat and skins (although, in most cases, levels of offtake due to hunting are not well quantified). The two forms most at risk are P. r. tephrosceles (which also suffers exceptionally high rates of predation from Chimpanzees) and P. r. rufomitratus, although P. r. tholloni is also certainly at risk

P. r. rufomitratus appears to have declined as a result of several causes: (a) drastic changes in vegetation due to dam construction, irrigation projects, and water diversion which changed the water table; (b) forest clearance for agriculture; (c) fires eroding levee forests; (d) degradation due to livestock and wood collection; (e) selective felling of Ficus trees for canoes; and (f) hunting. Because all remaining forest patches inhabited by colobus are small and seriously threatened, the population is highly vulnerable. The proposed Tana Integrated Sugar Project in Tana River and Lamu Districts threatens more than 200 km² of semi-natural habitat in the area.

The main threat to P. r. tephrosceles is habitat loss through selective logging of mature forest for timber, conversion to agricultural land, the production of charcoal, and forest fires. To some degree, hunting for meat and skins remains a threat (e.g., around Mbizi; Davenport et al. 2007). The taxon also appears to be heavily predated by chimpanzees. At Ngogo in Kibale National Park, the colobus live with the largest community of chimps recorded anywhere. They form huge hunting parties against the reds that result in the highest hunting success rate known for any large vertebrate predator (T. Struhsaker pers. comm.). The population in Gombe National Park appears to be seriously threatened with extinction because of predation by chimpanzees and because of the very small size (ca. 80 km²) and isolation of the Gombe park (Struhsaker 2005).

P. r. tholloni is vulnerable to hunting which has increased markedly since the Congo war (1996-2003), and habitat loss for timber and agricultural land likely effects some populations locally. It is known to be extensively hunted throughout its range (J. Thompson pers. comm.); A. Vesper (pers. comm.) reports that between the Tshuapa and the Lomami Rivers they are usually one of the first primates hunted out because they are so large and slow to flee.

The status of most of the remaining taxa included here is poorly known.

This taxon is listed on Appendix I of CITES and on Class B of the African Convention on the Conservation of Nature and Natural Resources. It is present in several protected areas across its range, and at least two of these, Kibale National Park and the Tana River Primate Reserve, are the last true bastions for the survival of P. r. tephrosceles and P. r. rufomitratus, respectively (see below).

Approximately 40% of the population of P. r. rufomitratus occurs within 13 km² of forest within the 169 km² Tana River Primate National Reserve. Stringent habitat protection is required and there is a need to re-establish the Mchelo Research Station.

P. r. tephrosceles is present in the 766 km² Kibale Forest National Park in Uganda, which may contain the only viable population; hunting by humans is virtually non-existant in this park (Struhsaker 2005). It is also present in the Gombe and Mahale National Parks in Tanzania. Long-term monitoring of the Ngogo situation is required, as well as a comprehensive, long-term monitoring programme for the colobus throughout Kibale. Kibale has the largest and perhaps only viable population of P. r. tephrosceles (although the population in Mbizi exceeds 1,000), and is the last hope for conservation of this taxon.

The southernmost population in the Mbizi forest should be protected; this is the only remaining montane forest of any size in Ufipa, and the only source of water for Sumbawanga’s growing population. There is also a need for immediate intervention if Mbuzi is not to be lost completely following the recent fate of both the Misheta and Nsangu forests. The forest patch is very small, isolated and has no protected status or management (Davenport et al. 2007).

P. r. tholloni is present in the Salongo National Park.

The range of P. r. oustaleti overlaps with the Okapi Faunal Reserve in DR Congo, and the proposed Mbaere-Bodingue national park in CAR.

P. r. ellioti may persist in the Semliki Forest Reserve, Uganda, and is possibly found in the Kahuzi-Beiga and Maiko National Parks, Democratic Republic of Congo.

The subspecies P. r. permentieri and P. r. langi are not known to occur in any protected areas.

The taxonomy of this species is extremely complex and much debated (see Struhsaker and Grubb in press; Groves in press; and references therein), and in need of urgent revision.

Maisels, F., Gautier-Hion, A. and Gautier, J. P. 1994. Diets of two sympatric colobines in Zaire: More evidence on seed-eating in forests on poor soils. International Journal of Primatology 15: 681–701.

Marsh, C. W. 1978. Ecology and social organization of the Tana River red colobus (Colobus badius rufomitratus). Ph.D. dissertation, University of Bristol.